Emergency Duties and Deaths from Heart Disease among Firefighters in the United States n engl j med 356;12 www.nejm.org march 22, 2007 1207 The new england journal of medicine established in 1812 march 22, 2007 vol. 356 no. 12 Emergency Duties and Deaths from Heart Disease among Firefighters in the United States Stefanos N. Kales, M.D., M.P.H., Elpidoforos S. Soteriades, M.D., Sc.D., Costas A. Christophi, Ph.D., and David C. Christiani, M.D., M.P.H. A BS TR A C T From the Cambridge Health Alliance, Harvard Medical School, Cambridge, MA (S.N.K.); the Department of Environmen- tal Health, Harvard School of Public Health, Boston (S.N.K., E.S.S., D.C.C.); the Pulmonary and Critical Care Unit, Massachusetts General Hospital, Boston (D.C.C.); the Center for Occupational and Environmental Medicine, Kindred Hos- pital Northeast, Braintree, MA (D.C.C.); and the Cyprus International Institute for the Environment and Public Health in association with the Harvard School of Public Health, Nicosia, Cyprus (C.A.C.). Address reprint requests to Dr. Kales at the Cambridge Health Alliance, Employee Health and Industrial Medicine, Lee B. Macht Bldg., Rm. 427, 1493 Cambridge St., Cambridge, MA 02139, or at skales@ challiance.org. N Engl J Med 2007;356:1207-15. Copyright © 2007 Massachusetts Medical Society. Background Heart disease causes 45% of the deaths that occur among U.S. firefighters while they are on duty. We examined duty-specific risks of death from coronary heart disease among on-duty U.S. firefighters from 1994 to 2004. Methods We reviewed summaries provided by the Federal Emergency Management Agency of the deaths of all on-duty firefighters between 1994 and 2004, except for deaths associated with the September 11, 2001, terrorist attacks. Estimates of the propor- tions of time spent by firefighters each year performing various duties were obtained from a municipal fire department, from 17 large metropolitan fire departments, and from a national database. Odds ratios and 95% confidence intervals for death from coronary heart disease during specific duties were calculated from the ratios of the observed odds to the expected odds, with nonemergency duties as the reference cat- egory. Results Deaths from coronary heart disease were associated with suppressing a fire (32.1% of all such deaths), responding to an alarm (13.4%), returning from an alarm (17.4%), engaging in physical training (12.5%), responding to nonfire emergencies (9.4%), and performing nonemergency duties (15.4%). As compared with the odds of death from coronary heart disease during nonemergency duties, the odds were 12.1 to 136 times as high during fire suppression, 2.8 to 14.1 times as high during alarm response, 2.2 to 10.5 times as high during alarm return, and 2.9 to 6.6 times as high during physical training. These odds were based on three estimates of the time that firefighters spend on their duties. Conclusions Certain emergency firefighting duties were associated with a risk of death from coronary heart disease that was markedly higher than the risk associated with nonemergency duties. Fire suppression was associated with the highest risk, which was approximately 10 to 100 times as high as that for nonemergency duties. Copyright © 2007 Massachusetts Medical Society. All rights reserved. Downloaded from www.nejm.org at RIKSHOSPITALET HF on February 18, 2008 . T h e ne w eng l a n d jo u r na l o f m e d icin e n engl j med 356;12 www.nejm.org march 22, 2007 1208 F irefighting is known to be a dan- gerous occupation. What is less appreciated is that the most frequent cause of death among firefighters is heart disease rather than burns or smoke inhalation. Cardiovascular events, largely due to coronary heart disease, account for 45% of deaths among firefighters on duty. 1,2 In contrast, such events account for 22% of deaths among police officers on duty, 11% of deaths among on-duty emergency medical services work- ers, and 15% of all deaths that occur on the job. 2,3 The high rate of death from cardiovascular causes among firefighters raises questions about contrib- uting factors. Possible factors, such as physical ex- ertion, emergency responses, and dangerous du- ties, are not unique to firefighting; they are also characteristic of the work performed by police of- ficers, military personnel, and persons in various other occupations. 4,5 Various biologically plausible explanations for the high mortality from cardiovascular events among firefighters have been proposed. These explanations include smoke and chemical expo- sure, irregular physical exertion, the handling of heavy equipment and materials, heat stress, shift work, a high prevalence of cardiovascular risk fac- tors, and psychological stressors. 6-13 Given these occupational risks, 37 U.S. states and 2 Canadian provinces provide benefits to firefighters in whom certain cardiovascular diseases have developed. 14 Nevertheless, the evidence linking firefighting to cardiovascular disease continues to be debat- ed. 15-17 Therefore, whether deaths from coronary heart disease among firefighters are truly precipi- tated by their work and, if so, by which duties, remain important questions. The findings in our previous case–control study of 52 deaths from coronary heart disease among on-duty firefighters provided preliminary evidence that coronary events may be triggered by specific firefighting duties. 18 First, the circadian pattern of deaths from coronary heart disease par- alleled the pattern of emergency-response dis- patches. Second, elevated risks of death were as- sociated with fire suppression, alarm response, and physical training. To confirm these findings and further explore duty-specific risk factors for death from coronary heart disease, we conducted a study of all deaths that occurred among on-duty firefighters in the United States between 1994 and 2004. Me t hods Deaths among Firefighters The U.S. Fire Administration, a branch of the Federal Emergency Management Agency, collects narrative summaries for all reported deaths as- sociated with firefighting in the United States. From these publicly available summaries, we ex- amined data on all deaths that occurred between January 1, 1994, and December 31, 2004. 2,19 The data included all firefighters who died while on duty, who became ill while on duty and later died, and who died within 24 hours after an emergency response or training. We excluded deaths that oc- curred during the first 48 hours after the Septem- ber 11, 2001, terrorist attacks. To extract study data, two reviewers indepen- dently examined the summary of each reported death that occurred while the firefighter was on duty. A third reviewer resolved any classifications that were not concordant between the first two reviewers. On the basis of the narrative reports, each death was classified as due to cardiovascular causes or to noncardiovascular causes. We then excluded those cases in which death occurred more than 24 hours after the on-duty incident or in which death resulted from a cardiovascular problem other than coronary heart disease (e.g., certain arrhythmias, stroke, aneurysm, or genetic cardiomyopathy). All records of deaths that were classified by this process as being due to coronary heart dis- ease were selected for further study. Data extract- ed from these records included the firefighter’s age, sex, and job status (professional or volun- teer); the date, cause, and mechanism of death; and the city and state of the fire department. Duties at the Time of Death On the basis of the summary report of each death, the deaths were classified according to the spe- cific duty performed during the onset of symp- toms or immediately preceding sudden death. These categories were fire suppression; alarm re- sponse; alarm return; physical training; emergen- cy medical services, rescues, and other nonfire emergencies; and nonemergency duties. A death was classified as being associated with fire sup- pression if it occurred while the person was fight- ing a fire or at the scene of a fire after its sup- pression. Alarm response involved responses to Copyright © 2007 Massachusetts Medical Society. All rights reserved. Downloaded from www.nejm.org at RIKSHOSPITALET HF on February 18, 2008 . De aths from He a rt Disease a mong Firefighters n engl j med 356;12 www.nejm.org march 22, 2007 1209 emergency incidents, including false alarms. Alarm return included all events that occurred during the return from incidents and those that occurred within several hours after an emergency call. Physical training included all job-related physical- fitness activities, physical-abilities testing, and simulated or live fire, rescue, emergency, and search drills. We grouped together emergency medical services, rescues, and other nonfire emer- gencies in a separate category. Finally, we classi- fied all of the following activities as nonemergen- cy duties: administrative and fire-station tasks, fire prevention, inspection, maintenance, meet- ings, parades, and classroom activities. Time Spent on Specific Duties We used data from several sources to estimate the average annual proportion of time that fire- fighters spend in each category. First, we direct- ly derived point estimates from a municipal fire department (Cambridge Fire Department, Cam- bridge, MA), using fiscal year 2002 data, as in our previous study. 18 For Cambridge firefighters, the following information was available: the number of firefighters, the total number of alarms and emergency responses, the distribution of emer- gency calls and dispatches by hour of the day, a breakdown of the types of incidents involved in fire and nonfire emergency responses, the average time spent per incident and the average response time, and the estimated number of hours spent each week in training and fire-prevention activities. We refer to these data as the municipal estimate. Second, to conduct a sensitivity analysis, we obtained two additional sets of estimates, one representing a level of emergency activity that was higher than that of the Cambridge Fire Depart- ment and the other representing a lower level of emergency activity. These estimates were derived with the use of data for the population served, the numbers of uniformed officers, and the num- ber of emergency incidents and the types of inci- dents classified as fire and nonfire emergencies. To characterize the largest and busiest fire de- partments, an estimate was developed from 2005 survey data provided by the International Associa- tion of Fire Fighters (Moore-Merrell L: personal communication) for 17 large urban and suburban fire departments (the large metropolitan esti- mate). To represent firefighters in smaller com- munities with lower levels of emergency activity, an estimate was developed from nationwide Na- tional Fire Protection Association surveys conduct- ed from 1994 to 2003 (the national estimate). 20 Statistical Analysis We made the initial assumption that if specific firefighting duties do not have a significant effect on the risk of death from coronary heart disease, then the number of such deaths that occur dur- ing any given firefighting duty should be directly proportional to the amount of time spent per- forming that duty. For example, if 10% of a fire- fighter’s time is spent in responding to alarms, 10% of deaths from coronary heart disease should occur during alarm response. We then sought to determine whether this expected pattern is or is not supported by the actual data. Using the chi-square goodness-of-fit test, we assessed whether the distribution of actual deaths associated with each duty was the same as that of expected deaths, based on the estimates of the average time dedicated to each firefighting duty. We used the three different time estimates (from the municipal, large metropolitan, and national data) to calculate the ratios of actual to expected deaths for each firefighting duty. The 95% confi- dence intervals (CIs) for these ratios were calcu- lated on the basis of the multinomial distribu- tion. Odds ratios for death from coronary heart disease during specific duties were calculated from the ratios of the observed to expected odds, with nonemergency duties used as the reference category. The 95% CIs for the estimated odds ratios were calculated with the use of the bino- mial distribution. Using data from the 2000 firefighters census, 21 which stratifies firefighters according to their age (in decades) and job status (professionals or vol- unteers), we calculated the rates of death from coronary heart disease for specific duties accord- ing to age and job status. Our calculations were based on death counts in each category per 1 mil- lion person-years of risk, derived from the average number of firefighters at risk in each subgroup over the 11-year period of observation. Analyses were performed with the use of SAS software for Windows (version 8.02, SAS Insti- tute), and StatXact (version 6.0). A P value of less than 0.05 was considered to indicate statistical significance, and all statistical tests for differ- ences were two-sided. Copyright © 2007 Massachusetts Medical Society. All rights reserved. Downloaded from www.nejm.org at RIKSHOSPITALET HF on February 18, 2008 . T h e ne w eng l a n d jo u r na l o f m e d icin e n engl j med 356;12 www.nejm.org march 22, 2007 1210 R es ult s Between January 1, 1994, and December 31, 2004, 1144 firefighter deaths were reported to the U.S. Fire Administration. We classified 449 deaths as due to coronary heart disease (39%). Of these deaths from coronary heart disease, 144 (32%) occurred during fire suppression, 138 (31%) oc- curred during alarm response or return, and the remaining 167 (37%) occurred during other duties ( Table 1 ). Table 2 shows the estimated proportion of time that firefighters spent each year in specific duties according to the three sources of fire- department activity data that we used. Among firefighters in Cambridge (our municipal data set), approximately 2% of duty time was spent in fire suppression. Among firefighters in our large metropolitan data set, approximately 5% of duty time was spent in fire suppression. Finally, among all firefighters in the United States (as represent- ed in our national data set), approximately 1% of duty time was spent in fire suppression. Table 3 shows the frequency of observed deaths from coronary heart disease according to duty as compared with the expected frequency. The ob- served distribution of deaths was significantly dif- ferent from the expected distribution based on the estimates from each of the three data sources (P< 0.001 for the three comparisons). The ratios of ob- served to expected deaths associated with the vari- ous duties of firefighters were consistently higher than 1, with the exception of nonfire emergencies and nonemergency duties. Although 32% of deaths occurred during fire suppression, this activity was estimated to account for as little as 1 to 5% of the average firefighter’s professional time per year, so this duty was associated with the most significant- ly elevated ratios of observed to expected deaths. Table 1. Deaths from Coronary Heart Disease among Firefighters, Classified According to Duty at the Time of Death.* Duty Deaths (N = 449) no. (%) Fire suppression 144 (32.1) Alarm response 60 (13.4) Alarm return 78 (17.4) Physical training 56 (12.5) Emergency medical services and other nonfire emergencies 42 (9.4) Fire-station and other nonemergency duties 69 (15.4) * Data are based on narrative summaries from the records of the U.S. Fire Ad- ministration, Federal Emergency Management Agency, for the period from January 1, 1994, to December 31, 2004. 19 Table 2. Fire Service Activity and the Estimated Proportion of Time Spent in Specific Firefighting Duties.* Variable Municipal Fire Department Large Metropolitan Fire Departments National Data Fire service activity Population served (no.) 101,355 760,935±888,916 280,000,000 Uniformed firefighters (no.) 274 1063±785 1,082,855±14,446 Population served per firefighter (no.) 370 655±218 259±3 Emergency incidents (no./firefighter/yr) 44 92±24 18±2 Fire incidents (no./firefighter/yr) 2.0 7.0±6.3 1.7±0.1 Duties (% of annual time) Fire suppression 2 5 1 Alarm response 6 9 4 Alarm return 10 15 7 Physical training 8 8 8 Emergency medical services and other nonfire emergencies 23 34 15 Fire-station and other nonemergency duties 51 29 65 * Plus–minus values are means ±SD. Municipal data are from the Cambridge Fire Department, Cambridge, Massachusetts (2002). 18 Data for large metropolitan fire departments are from surveys of 17 large metropolitan fire departments conducted by the International Associ- ation of Fire Fighters (2005) (Moore-Merrell L: personal communication). National data are from annual national surveys conducted by the National Fire Protection Association (1994 through 2003). 20 Copyright © 2007 Massachusetts Medical Society. All rights reserved. Downloaded from www.nejm.org at RIKSHOSPITALET HF on February 18, 2008 . De aths from He a rt Disease a mong Firefighters n engl j med 356;12 www.nejm.org march 22, 2007 1211 Table 4 includes the odds ratios and 95% CIs for the risk of death from coronary heart disease among firefighters engaged in each emergency duty and physical training as compared with the reference category of nonemergency tasks. On the basis of the three estimates of the time that fire- fighters spent on particular duties, death from coronary heart disease was 12 to 136 times as likely to occur during fire suppression as during nonemergency duties. An increased risk was also consistently observed for other emergency duties, as compared with nonemergency duties; the risk was increased by a factor of 2.8 to 14.1 during alarm response, 2.2 to 10.5 during alarm return, and 2.9 to 6.6 during physical training. Figure 1A shows the risk of death from coro- nary heart disease per 1 million firefighters per year (deaths per 1 million person-years) for each duty according to age group, and Figure 1B shows the risk of death according to job status (volun- teer or professional). As might be expected, the risk of coronary heart disease generally increased with age for each type of duty, whereas the results for job status were mixed. Di s cus sion In this study, we used data from a nationwide reg- istry of deaths among firefighters over an 11-year period and estimates from three different sources of time spent in various firefighting duties to estimate the duty-specific risks of death from coronary heart disease among firefighters. As com- pared with nonemergency duties, certain emer- gency duties and physical training were associat- ed with an increased risk of death from coronary heart disease among firefighters. These findings are consistent with those of our previous, smaller study 18 and with an analysis of cardiac events that led to retirement from firefighting. 22 Fire suppression, which represents only about 1 to 5% of firefighters’ professional time each year, accounted for 32% of deaths from coronary heart disease and was associated with a risk of death from coronary heart disease that was ap- proximately 10 to 100 times as high as the risk associated with nonemergency duties. We think that the most likely explanation for these find- ings is the increased cardiovascular demand of fire suppression. 8,11 The risk of coronary heart disease events dur- ing fire suppression may be increased because Table 3. Observed and Expected Distributions of Deaths from Coronary Heart Disease among On-Duty Firefighters, According to Duties.* Duty Observed Deaths (N = 449) Expected Deaths Municipal Fire Department Large Metropolitan Fire Departments National Data Expected Deaths (N = 449) Observed:Expected Deaths Expected Deaths (N = 449) Observed:Expected Deaths Expected Deaths (N = 449) Observed:Expected Deaths no. (%) no. (%) ratio (95% CI) no. (%) ratio (95% CI) no. (%) ratio (95% CI) Fire suppression 144 (32.1) 9.0 (2) 16.0 (13.2–19.1) 22.4 (5) 6.4 (5.3–7.6) 4.5 (1) 32.1 (26.4–38.1) Alarm response 60 (13.4) 26.9 (6) 2.2 (1.6–3.0) 40.4 (9) 1.5 (1.1–2.0) 18.0 (4) 3.3 (2.4–4.5) Alarm return 78 (17.4) 44.9 (10) 1.7 (1.3–2.2) 67.4 (15) 1.2 (0.9–1.5) 31.4 (7) 2.5 (1.8–3.2) Physical training 56 (12.5) 35.9 (8) 1.6 (1.1–2.1) 35.9 (8) 1.6 (1.1–2.1) 35.9 (8) 1.6 (1.1–2.1) Emergency medical services and other nonfire emergencies 42 (9.4) 103.3 (23) 0.4 (0.3–0.6) 152.7 (34) 0.3 (0.2–0.4) 67.4 (15) 0.6 (0.4–0.9) Fire-station and other nonemergency duties 69 (15.4) 229.0 (51) 0.3 (0.2–0.4) 130.2 (29) 0.5 (0.4–0.7) 291.8 (65) 0.2 (0.2–0.3) * Municipal data are from the Cambridge Fire Department, Cambridge, Massachusetts (2002). 18 Data for large metropolitan fire departments are from surveys of 17 large metropolitan fire departments conducted by the International Association of Fire Fighters (2005) (Moore-Merrell L.: personal communication). National data are from annual national surveys con- ducted by the National Fire Protection Association (1994 through 2003). 20 Copyright © 2007 Massachusetts Medical Society. All rights reserved. Downloaded from www.nejm.org at RIKSHOSPITALET HF on February 18, 2008 . T h e ne w eng l a n d jo u r na l o f m e d icin e n engl j med 356;12 www.nejm.org march 22, 2007 1212 many firefighters lack adequate physical fitness, have underlying cardiovascular risk factors, and have subclinical or clinical coronary heart disease. Even new firefighter recruits may be overweight and have low-to-normal aerobic capacities. 23 Such problems are compounded during career tenure because more than 70% of fire departments lack programs to promote fitness and health. 1 Most fire departments do not require firefighters to ex- ercise regularly, undergo periodic medical exami- nations, or have mandatory return-to-work eval- uations after a major illness. In addition, several studies have shown the high prevalence of risk factors for cardiovascular disease among fire- fighters 24-29 as well as lower-than-expected exer- cise tolerance. 30,31 Moreover, two studies have shown that among firefighters who had fatal events 18 or nonfatal events 22 related to coronary heart disease while on duty, 26% and 18%, respec- tively, had previously received a diagnosis of coro- nary heart disease, peripheral vascular disease, or cerebrovascular disease, and among the remain- der, smoking, hypertension, and diabetes melli- tus were significantly more prevalent than among active firefighters in the control group. Likewise, in our study, the risk of death from coronary heart disease increased with age for all types of duty. Unexpectedly, professional and volunteer firefighters had different risks of death from coronary heart disease, depending on the type of duty performed, although for both groups, the risk was highest during fire suppression. In parallel with our finding of a significantly increased risk of death from coronary heart dis- ease during fire suppression, as compared with nonemergency duties, the risk was significantly elevated during physical training. This finding is consistent with investigations implicating intense physical activity as a strong triggering factor, es- pecially among physically inactive persons. 32-35 Also consistent with the triggering hypothesis and with research documenting increased heart rates among firefighters responding to alarms 8,9 was our finding that the risk of death from coro- nary heart disease associated with alarm response and alarm return was approximately five to seven times as high as that associated with nonemer- gency duties. Emergency medical services and other nonfire emergency responses were not as- sociated with a significant increase in risk. These findings are consistent with the much lower pro- portion of deaths from coronary heart disease among emergency medical services workers who are not firefighters 3 than among firefighters, and may reflect a lower level of exposure to physically demanding emergencies. One limitation of our study is that the esti- mates of odds ratios for specific job duties are based on fairly wide approximations of time spent on different duties. The average work year of a professional firefighter in a major urban center is probably much different from that of a rural volunteer firefighter. In addition, there have been few if any comprehensive studies of how fire- Table 4. Risk of Death from Coronary Heart Disease among Firefighters Engaged in Emergency Duties and Physical Training as Compared with Firefighters Engaged in Nonemergency Duties.* Duty Municipal Fire Department Large Metropolitan Fire Departments National Data Odds Ratio (95% CI) P Value Odds Ratio (95% CI) P Value Odds Ratio (95% CI) P Value Fire suppression 53 (40–72) <0.001 12.1 (9.0–16.4) <0.001 136 (101–183) <0.001 Alarm response 7.4 (5.1–11) <0.001 2.8 (1.9–4.0) <0.001 14.1 (9.8–20.3) <0.001 Alarm return 5.8 (4.1–8.1) <0.001 2.2 (1.6–3.1) <0.001 10.5 (7.5–14.7) <0.001 Emergency medical services and other nonfire emergencies 1.3 (0.9–2.0) 0.16 0.5 (0.3–0.8) <0.001 2.6 (1.8–3.9) <0.001 Physical training 5.2 (3.6–7.5) <0.001 2.9 (2.0–4.2) <0.001 6.6 (4.6–9.5) <0.001 Nonemergency duties (fire sta- tion and other) 1.0 1.0 1.0 * Municipal data are from the Cambridge Fire Department, Cambridge, Massachusetts (2002). 18 Data for large metropol- itan fire departments are from surveys of 17 large metropolitan fire departments conducted by the International Associ- ation of Fire Fighters (2005) (Moore-Merrell L.: personal communication). National data are from annual national sur- veys conducted by the National Fire Protection Association (1994 through 2003). 20 Copyright © 2007 Massachusetts Medical Society. All rights reserved. Downloaded from www.nejm.org at RIKSHOSPITALET HF on February 18, 2008 . De aths from He a rt Disease a mong Firefighters n engl j med 356;12 www.nejm.org march 22, 2007 1213 fighters spend their time. Our estimate of the increase in risk is therefore subject to considera- ble uncertainty. However, even in the most conser- vative scenario (with the use of the time estimates from the large metropolitan fire departments), the risks associated with fire suppression remained remarkably high and were also significantly in- creased for alarm response, alarm return, and physical training. Also, our three sets of risk estimates are not based on three completely distinct calculations. In each case, one set of national figures for “ob- served” deaths was used, and the resulting odds ratios represent risk relative to nonemergency duties, not absolute risks for one group of fire- fighters as compared with another. Our results should therefore not be used to suggest that the risk of death from coronary heart disease during fire suppression is higher in a small community fire department than in a large metropolitan fire department. Instead, the three calculations pro- vide a range of estimates of the average risk for firefighters nationwide. Because only 14% of fire- fighters in the United States serve populations larger than 100,000 residents, 21 we think that the average risk for most firefighters probably falls between the risk based on estimates of time spent in particular duties that were derived from a single municipal fire department and the risk based on the nationwide time estimates. Our es- timate that fire suppression accounts for 1 to 2% of annual work time (for the nationwide and mu- nicipal scenarios, respectively) is consistent with a study of a large fire department in Montreal, 36 where fire suppression accounted for 0.7 to 2.5% of annual work time. A second limitation of our study was the need to base our evaluation on brief narratives, which lacked autopsy information for some of the deaths. However, the misclassification of deaths due to inadequate information would have contributed to a random error, most likely diluting the results of our study toward the null hypothesis. Although 26 deaths from cardiovascular but not coronary heart disease were excluded, this small number was unlikely to bias the overall results in a spe- cific direction. A third limitation of our analysis was the starting assumption that the number of deaths from coronary heart disease that occur during any given firefighting duty should be directly pro- portional to the amount of time spent perform- ing that duty. It is well established, for example, that the risk of coronary heart disease events var- ies according to the time of day, 37 as well as the season of the year. 38 In this study, we could not examine the circadian pattern of deaths. How- ever, in our previous, smaller study 18 and in an- other, 10-year analysis, 2 67 to 77% of deaths from cardiac causes among on-duty firefighters oc- curred between noon and midnight, as did more than 60% of emergency responses. This pattern is in stark contrast to the peak period for cardio- vascular events in the general population, which is 6 a.m. to noon. With respect to season, deaths from cardiac causes among firefighters are most frequent in the winter, as they are in the general population. When we analyzed duty-specific risks 22p3 20–39 Yr 40–49 Yr 50–59 Yr ≥60 Yr Volunteer Professional Annual No. of Deaths per 1 Million Firefighters 40 30 10 50 20 0 Fire Suppression Alarm Response Alarm Return Physical Training Emergency Medical Services Fire- Station Duty 60 Annual No. of Deaths per 1 Million Firefighters 12 10 2 6 4 14 8 0 Fire Suppression Alarm Response Alarm Return Physical Training Emergency Medical Services Fire- Station Duty 16 AUTHOR: FIGURE: JOB: ISSUE: 4-C H/T RETAKE SIZE ICM CASE EMail Line H/T Combo Revised AUTHOR, PLEASE NOTE: Figure has been redrawn and type has been reset. Please check carefully. REG F Enon 1st 2nd 3rd Kales 1 of 1 03-22-07 ARTIST: ts 35612 A B Figure 1. Duty-Specific Annual Risk of Death from Coronary Heart Disease among Firefighters, According to Age (Panel A) and Job Status (Panel B). Copyright © 2007 Massachusetts Medical Society. All rights reserved. Downloaded from www.nejm.org at RIKSHOSPITALET HF on February 18, 2008 . T h e ne w eng l a n d jo u r na l o f m e d icin e n engl j med 356;12 www.nejm.org march 22, 2007 1214 separately for each of the four seasons, however, the resulting point estimates for each duty re- mained similar in magnitude and close to the range of our original confidence intervals. Final- ly, although we cannot completely account for the effects of the time of day and season, the high- est estimates of these effects on event rates are at least an order of magnitude smaller than the relative risks we observed for specific duties. In conclusion, we analyzed nationwide data on deaths among firefighters, as well as three separate estimates of time spent in various fire- fighting duties, to determine the duty-specific risks of death from coronary heart disease among firefighters. Our analysis showed that specific duties, especially fire suppression but also alarm response, alarm return, and physical training, are associated with significant increases in risk. Supported in part by grants from the National Institute for Occupational Safety and Health (T42/CCT122961-02, to Dr. Kales) and the Massachusetts Public Employees Retirement Administration Commission (to Dr. Kales). The funders had no involvement in the study design, data collection and analysis, writing of the paper, or decision to submit the paper for publi- cation. Dr. Kales and Dr. Christiani report serving as paid expert wit- nesses, independent medical examiners, or both in workers’ com- pensation and disability cases, including cases involving fire- fighters. No other potential conflict of interest relevant to this article was reported. We thank Ken Pitts, John Gelinas, and Lori Moore-Merrell for providing fire-department incident, response, activity, and sur- vey data. References Fahy RF. U.S. firefighter fatalities due to sudden cardiac death, 1995–2004. Quincy, MA: National Fire Protection As- sociation, June 2005. 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Emergency Duties and Deaths from Heart Disease among Firefighters in the United States n engl j med 356;12 www.nejm.org march 22, 2007 1207 The new england journal of medicine established. with the triggering hypothesis and with research documenting increased heart rates among firefighters responding to alarms 8,9 was our finding that the risk of death from coro- nary heart disease. developed. 14 Nevertheless, the evidence linking firefighting to cardiovascular disease continues to be debat- ed. 15-17 Therefore, whether deaths from coronary heart disease among firefighters